"There are many orators in the temple."
Translation:Multi oratores sunt in templo.
I don't think there is anything wrong with that word order.
It is likely that it is just not yet an accepted answer (many likely get missed just due to the freer word order). I would suggest reporting that solution should it not be accepted the next time you get this (if it is still not accepted, just ensure everything in your answer is correct when you report it).
in with an ablative specifies a static location, no movement. They are located in the temple, hence the in templo.
in with an accusative specifies a movement into a location. If they were moving into the temple then in templum could be used. Multi oratores in templum eunt -> 'Many orators are going into the temple'.